​The Sandwatch Foundation partners with innovative erosion control project in Southern Senegal


April 2022 – Professor Patrick Chevalier, an Associé at the Université de Lille, France has been in discussions with The Sandwatch Foundation, regarding integrating our methodology for involving local communities in direct participation in the scientific monitoring of coastal environmental issues with his current project in the Casamance region of Southern Senegal.

The project involves efforts to mitigate shoreline erosion through a very innovative erosion control programme of his design (details below), whereby communities located on several erosion prone islands in the Casamance region, will participate in the construction and monitoring of “semi-permeable groynes” using locally available and renewable organic materials.

Prof Chevalier, who works with Groupement Des Educateurs Sans Frontieres (GREF) and the Iles Casamance Organiaztion with support from the French Embassy in Dakar, will be returning to Senegal in May, 2022 to see how the groynes he and his team built last November on the islands of Diogué, Ehidj and Wendaye as pilot projects have held up and to measure how successful they have been in preventing and even reversing coastal erosion at the test areas.

In addition, during this trip Prof Chevalier hopes to expand the project to several other islands and mobilize many of the local students and educators in assisting with the project and conducting vital ongoing maintenance and monitoring of the groynes over time. Prof Chevalier has identified at least two local schools that he hopes to introduce The Sandwatch Foundation's M.A.S.T. methodology to, that being Monitor the environment, Analyze results, Share findings and Take action.

For our part, The Sandwatch Foundation will offer Prof Chevalier as much support as we can including French copies of the Sandwatch manual, remote advice and possibly training via Zoom and access to our online “Beach Records” platform via a French language app we are currently developing specifically for this purpose.

The Sandwatch Foundation's “Beach Records” platform is essentially a simplified, easy to use database designed for non-technical, citizen scientists to record basic observations and measurements of their local beach. In this way Prof Chevalier and his team can monitor how their tests sites are faring even when they are not there personally and of course it also provides local teachers and students a simple way to better understand and have a real impact on their local environment and help preserve the traditional way of life on these threatened islands.

What are semi-permeable groynes?

In brief, to mitigate the effects of localized erosion, Professor Chevalier’s project calls for construction of “semi-permeable groynes” on threatened beaches. Groynes, traditionally are a parallel series of solid low walls or sturdy barriers built out into the sea from a beach to check erosion and capture drifting sand. But Prof Chevalier’s design aren’t “solid structures” which are very expensive to construct and can over time have adverse effects on long shore currents and on the deposition and erosion of sand. 

​Rather these groynes are constructed using simple wooden stakes, cut locally from invasive eucalyptus trees (not indigenous mangroves!) and then roughly layered with a loose mat of palm fronds. The loose mat of palm leaves, allows the groynes to be semi-permeable that is they don't radically impede the movement of sea water but rather just slow it down and trap some of the surf borne sand around them, which gradually builds up over time.  And as the groynes themselves are fully organic, they will gradually degrade and disappear over time, leaving behind large deposits of sand and even dunes which can be stabilized with vegetation and even mangroves which provide excellent long term resistance to coastal erosion.
Picture
Making the eucalyptus stakes
Picture
Driving the stakes into the sand
Below are links to several of Prof Chevalier’s papers showing full details of his designs and their construction in both French and English.  In addition, there are links to, two short videos which show the dramatic amount of coastal erosion in the Casamance region between 2006 and 2018 and the basic construction technique of the semi-permeable groynes by local villagers and fishermen.
https://vimeo.com/538307205
https://vimeo.com/658358143
Picture
Diagram of the groyne, showing the wooden stakes and the palm frond matting between them

​Prof. Chevalier's papers with details of his designs in French and English (PDF)...
Site pilote de lutte contre l’érosion 
Pilot site for erosion control: Diogué Island
LUTTER CONTRE L’ÉROSION AVEC LES ÉPIS PERMÉABLES
FIGHT AGAINST EROSION WITH PERMEABLE GROYNES
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​Note: In addition to The Sandwatch Foundation assisting Prof Chevalier in the Casamance region of Senegal, we are also currently working on a second project further to the north in the Dionewar region of Senegal.  This partnership is with the sustainable development and environmental organization Fii Laa Tékee (FLT) to assist local communities in combating beach erosion and shore up protection of the coastal environment via the NGO Nebeday and the  Dionewar's Environment Club. 

The Sandwatch Foundation looks forward in the coming months to assisting both Prof Chevalier and The FLT  and all their colleagues with their vitally important mission, so stay tuned for developments!